Relaxation dynamics of water in the aqueous Relaxation dynamics of water in the aqueous mixtures mixtures

of propylene glycol oligomers of propylene glycol oligomers at ambient and elevated pressureat ambient and elevated pressure

66thth International Discussion International Discussion Meeting on Relaxations in Meeting on Relaxations in

Complex SystemsComplex Systems, ROME 2009, ROME 2009

Katarzyna Katarzyna GrzybowskaGrzybowska

Institute of PhysicsInstitute of Physics

University of SilesiaUniversity of Silesiain Katowicein Katowice

POLANDPOLAND

Collaborators:Collaborators:

UniversityUniversity of Silesia of Silesia,, Poland:Poland:Marian PaluchMarian PaluchAndrzej GrzybowskiAndrzej GrzybowskiSSebastian ebastian Pawlus Pawlus

Università di Pisa,Università di Pisa, Italy:Italy:Simone CapaccioliSimone CapaccioliDaniele PrevostoDaniele PrevostoSergiy Sergiy AncherbakAncherbak

MaterialMolecular

weightMw [g/mol]

Number of mers

pStructural formula

dimer of propylene glycol

(DPG)134 2

trimer of propylene glycol

(TPG)192 3

PPG 400 400 ~ 7 OHO

OH

CH3

CH3p-1

OHO

OH

CH3

CH3

OO

CH3

CH3

OH

CH3

OH

To prepare water mixtures we used To prepare water mixtures we used polypropylene glycols (PPG) (=diols) of different polypropylene glycols (PPG) (=diols) of different

chain lengthschain lengths

Water mixtures Water mixtures of propylene glycol of propylene glycol

oligomersoligomersAt atmospheric pressure At atmospheric pressure it has been studied it has been studied

over 20 water mixtureover 20 water mixturess of polypropylene glycolsof polypropylene glycols

(DPG, TPG(DPG, TPG,, andand PPG PPG 400)400) with different with different contentcontent of of

waterwaterFor the mixture For the mixture

PPG 400 + 26%HPPG 400 + 26%H22O O it has been it has been performed performed dielectric dielectric

measurements measurements at elevated pressure: at elevated pressure:

P = 360 MPa P = 360 MPa P = 500 MPaP = 500 MPaP = 1800 MPaP = 1800 MPa

26 0.89

Water significantly changesWater significantly changes the relaxation dynamics of the relaxation dynamics of PPGPPG::

Dielectric measurements of water mixtures of Dielectric measurements of water mixtures of PPG at P=0.1 MPa PPG at P=0.1 MPa

DPG+HDPG+H22O (O (liquidliquid

state)state) α-relaxationν-ν-

relaxation

TPG+HTPG+H22O (glassy O (glassy state)state) ν-ν-

relaxation

1) Appearing of a new additional 1) Appearing of a new additional - - relaxation processrelaxation process

--procesprocesss

ν-process reflects mainly ν-process reflects mainly the water dynamics in the the water dynamics in the

mixturemixture

The spectacular increase in dielectric The spectacular increase in dielectric strenght Δεstrenght Δενν

with increasing of water content in with increasing of water content in solutionsolution

2) Even a small amount of water added to pure PPG 2) Even a small amount of water added to pure PPG results in a slowdown results in a slowdown of the of the -relaxation observed in anhydrous PPG and the -relaxation observed in anhydrous PPG and the drop of Δεdrop of Δε

Hindering of the reorientations of Hindering of the reorientations of PPGPPG OH groups by H-bonds OH groups by H-bonds

formed between water molecules formed between water molecules and OH groups of PPGand OH groups of PPG

νν--processprocess

PPG 400+HPPG 400+H22O (glassy O (glassy state)state)

--processprocess

-process originates from -process originates from some reorientations of some reorientations of terminal parts of PPG terminal parts of PPG

molecules containing OH molecules containing OH groupsgroupsK. Grzybowska, et al. J. Chem. Phys. 128 134904 (2008); K. Grzybowska, et al. J. Phys.:

Condens. Matter 19, 376105 (2007)K. Grzybowska, et al. J. Chem. Phys. 128 134904 (2008); K. Grzybowska, et al. J. Phys.: Condens. Matter 19, 376105 (2007)

Temeperature dependences of dielectric Temeperature dependences of dielectric relaxation times for water mixtures of PPG at relaxation times for water mixtures of PPG at

P=0.1 MPa P=0.1 MPa

VFT eq.

0

0TT

A

e

kT

Ea

e0

Arrhenius law

Activation enery EActivation enery Ea a of ν and of ν and -processes obtained -processes obtained at T<Tat T<Tgg from Arrhenius eq. vs mole fraction of from Arrhenius eq. vs mole fraction of

water at P=0.1 MPa water at P=0.1 MPa I. Takei, I. Takei, Physics and Physics and Chemistry of IceChemistry of Ice, , Cambiridge (2007)Cambiridge (2007)

R.P. Auty, R.H. R.P. Auty, R.H. Cole,Cole, J. Chem. Phys. 20, J. Chem. Phys. 20, 1309 (1952)1309 (1952)

S. S. Cerveny, Cerveny, et al.et al., , Phys. Phys. Rev. Lett. Rev. Lett. 9393, , 245702 (2004)245702 (2004)

α -process

νν--process

Dielectric spectra of the mixture PPG+26%HDielectric spectra of the mixture PPG+26%H22O O at high pressure at high pressure

α -α -processprocess

ν-ν-process

α –α –processprocess

ν-ν-process

(α(α--peak peak is hidden is hidden due to a high due to a high contribution contribution

of dc-conductivity to of dc-conductivity to ε”)ε”)

P=0.1 P=0.1 MPaMPa

P=500 P=500 MPaMPa

P=1.8 P=1.8 GPaGPa

P=500MPaT=-41oC

P=0.1 MPaT=-75oC

decadedecadePPG 400 + 26% PPG 400 + 26%

HH22OO

Near the glass transition, the ν- relaxation is less Near the glass transition, the ν- relaxation is less sensitive to changes sensitive to changes

of pressure and temperature than α- processof pressure and temperature than α- processProperty typical Property typical for JG-processfor JG-process

IIn this respect the νn this respect the ν--relaxation can be considered as a relaxation can be considered as a secondary relaxation reflecting some local dynamics of secondary relaxation reflecting some local dynamics of

water component in the aqueous mixturewater component in the aqueous mixture

the separation the separation between between

α and α and processes is processes is one decade greater in one decade greater in

the case of the case of measurement at 500 measurement at 500

MPa than that for MPa than that for ambientambient pressure pressure

process has the same sensitivity to pressure and temperature process has the same sensitivity to pressure and temperature like typical JG secondary relaxation in many glass forming-like typical JG secondary relaxation in many glass forming-

liquidsliquids

αα--processeprocesse

ss

VFT equation at T>Tg

for medium P

Tg(τα=100s)

Relaxation map for PPG 400+26%HRelaxation map for PPG 400+26%H22O at high O at high pressures pressures

Tg =267 K (P=1.8 GPa)

1.8GPa

Tg=267 K

PTPT

Pgg 1)(0

Tg(P=0) =193K, Π=298MPa, β =0,17

ττ cross cross

=Tcross

Arrhenius equation at T<Tg

for all P

pressure considerably pressure considerably influences the nature of influences the nature of --process dynamic crossoverprocess dynamic crossover

TTgg of the water mixture of the water mixture increase with increasing increase with increasing

PP

ν relaxation time ν relaxation time ((ττν crossν cross))

at the dynamic crossoverat the dynamic crossoverdecreases exponentially with decreases exponentially with

compressioncompression

τν cross(P→∞)=3s

EEaa of of -process in the liquid state of the -process in the liquid state of the mixturemixture

evaluated from Arrhenius eq. evaluated from Arrhenius eq. (for P=0.1 MPa and 1.8GPa at T>Tg) (for P=0.1 MPa and 1.8GPa at T>Tg)

and VFT eq. (for P=360 and 500 MPa at and VFT eq. (for P=360 and 500 MPa at TTgg=T=Tcrosscross) )

EEaa of of -process in the glassy state of -process in the glassy state of the mixturethe mixture

evaluated from Arrhenius eq.evaluated from Arrhenius eq.

R. Casalini, C. M. Roland, Phys. Rev. B 71, 014210 (2005)

Non-Non-associatassociat

ed ed

liquidsliquids

Unusual pressure dependences of Unusual pressure dependences of -process -process activation energies and fragility of the mixture activation energies and fragility of the mixture

PPG400+26%HPPG400+26%H22OO

Initially the increase in pressure can Initially the increase in pressure can facilitate the hydrogen bonds forming, facilitate the hydrogen bonds forming,

whereas P>1 GPa may significant whereas P>1 GPa may significant reducing of reducing of H-H-bonds bonds

in the water clusters in mixturein the water clusters in mixture

SUMMARYSUMMARYIt has been It has been found that pressure found that pressure considerably affects the relaxation considerably affects the relaxation dynamics of water mixture of PPG 400. dynamics of water mixture of PPG 400. • IIn the whole pressure range (0.1MPa-n the whole pressure range (0.1MPa-

1.8GPa1.8GPa) w) we observed the dynamic crossovere observed the dynamic crossover of of -relaxation-relaxation times times))

At medium pressuresAt medium pressures (360 and 500 MPa) (360 and 500 MPa),, --relaxationrelaxation times reveal times reveal fragile-to-strong fragile-to-strong dynamic crossoverdynamic crossover

X-Q. Chu X-Q. Chu et al.et al. , , http://shibayama.issp.utokyo.ac.jp/nagao/NSE2006/Abstracts/NSE2006_yoshida.pdf. http://shibayama.issp.utokyo.ac.jp/nagao/NSE2006/Abstracts/NSE2006_yoshida.pdf. (2008)(2008); ; L. Liu et al., Phys. Rev. Lett. 95 117802 (2005).

X-Q. Chu X-Q. Chu et al.et al. , , http://shibayama.issp.utokyo.ac.jp/nagao/NSE2006/Abstracts/NSE2006_yoshida.pdf. http://shibayama.issp.utokyo.ac.jp/nagao/NSE2006/Abstracts/NSE2006_yoshida.pdf. (2008)(2008); ; L. Liu et al., Phys. Rev. Lett. 95 117802 (2005).

Confined water in porous silica materialProtein hydration water

PPG 400 + 26% H2O

In contrary to confined water the dependence Tcross(P) for water mixture has an increasing character and we cannot relate it to the liquid-liquid phase transition line in a T-P plane.

In contrary to confined water the dependence Tcross(P) for water mixture has an increasing character and we cannot relate it to the liquid-liquid phase transition line in a T-P plane.

LDL

HDL

For water mixture, EEaa(P) (P) for the for the --relaxation is nonmonotonic and reveals a relaxation is nonmonotonic and reveals a maximum, while the Arrhenius activation maximum, while the Arrhenius activation energy for the confined water process energy for the confined water process decreases with increasing P at T<Tdecreases with increasing P at T<Tcrosscross..

For water mixture, EEaa(P) (P) for the for the --relaxation is nonmonotonic and reveals a relaxation is nonmonotonic and reveals a maximum, while the Arrhenius activation maximum, while the Arrhenius activation energy for the confined water process energy for the confined water process decreases with increasing P at T<Tdecreases with increasing P at T<Tcrosscross..

PPG 400 + 26% H2O

PPG 400 + 26% H2O2-D confined protein hydration water

For PPG400+26%H2O, the crossover relaxation time τν cross decreases exponentially with increasing P , whereas for confined water τcross(P)const.

For PPG400+26%H2O, the crossover relaxation time τν cross decreases exponentially with increasing P , whereas for confined water τcross(P)const.

Supercooled water in the mixture of PPG have different properties than Supercooled water in the mixture of PPG have different properties than pure supercooled confined water. Our findings indicate that pure supercooled confined water. Our findings indicate that process process

should be rather considered as a secondary relaxation reflecting some local should be rather considered as a secondary relaxation reflecting some local dynamics of water component in the aqueous mixturedynamics of water component in the aqueous mixture